This invention relates generally to a self-generating gas pressure apparatus such as an expandable pouch means positionable in a container containing a fluid so as to provide pressure on the fluid so that it can be dispensed from the container, and in particular to a method for gas generation employing gas-producing chemical reactants provided with a nucleating agent to enhance the speed and maintenance of gas production and resultant pressure within the apparatus.
The use of self-generating gas pressure apparatus in general within a container from which a fluid is to be dispensed under pressure is well-known in the art. U.S. Pat. Nos. 4,360,131, 4,376,500, 4,478,044 and 4,513,884, for example, describe various gas-generating pressure apparatus. Typically, an expandable closed vessel such as a pouch means having a plurality of internal compartments is employed, with the compartments having interfacing barriers or individualized walls formed by seals which are rupturable under pressure. Within adjacent compartments, for example, one such compartment will contain a first chemical compound and the second compartment will contain a second chemical compound. The particular compounds are chosen from among those which react with each other to form a gas. Thus, for example, one compartment may contain citric acid, while the other compartment contains sodium bicarbonate. When these two compounds mix with each other, they react to produce carbon dioxide. To accomplish such mixing in the expandable vessel, a trigger reaction is permitted to occur which subsequently causes the rupture of the seal which interfaces between the two adjacent compartments. This results in the mixture and reaction of the two compounds to produce a gas which expands the vessel to thereby apply pressure on the fluid within the container in which the expandable vessel is housed. A novel self-generating pressure applying means is taught in co-pending and commonly-assigned U.S. patent application Ser. No. 34,900, filed Apr. 6, 1987, incorporated herein by reference.
While gas pressure generation occurs as above described and is generally adequate as long as sufficient time passes between individual dispensing procedures to thereby achieve pressure regeneration from continued chemical reaction, such generation may not be rapid enough or sufficiently uniform to provide optimum pressure to the fluid to be dispensed from the containers during continued dispensing, resulting in a slow fluid flow from the container as the dispensing procedure continues. Accordingly, it is a primary object of the present invention to provide a self-generating gas pressure apparatus wherein gas formation occurs relatively rapidly and uniformly. Another object of the present invention is to provide apparatus wherein chemical compounds which react with each other to produce gas react in the presence of a nucleating agent. Yet another object of the present invention is to provide apparatus wherein caking of the nucleating agent employed as well as production of a stable foam during reaction of the chemical compounds is retarded. These and other objects of the present invention will become apparent throughout the description thereof.